This present invention relates to a ratchet wrench that includes a torque indicator that progressively indicates the amount of torque that is be exerted on the screw or bolt each time the wrench is rotated and then ratcheted back to its starting position. In particular, the present invention relates to dental ratchet wrench with torque indication for dentistry.
While ratchet wrenches have been used in the previously used in various fields including dentistry, it is particularly useful to know the amount of torque that each partial rotation and subsequent ratcheting of the wrench places on the screw or bolt. Thus, unlike a torque limiter, which does not allow the torque to exceed a certain amount, a need exists for a ratchet wrench having a torque indicator that progressively indicates the torque as it is being exerted on the bolt or screw. Further, a need exists for this device to be located in a relatively small housing especially when it is to be used in small regions, such as in the mouth.
This specification describes a ratchet wrench and a torque indicator combined concentrically in a single housing. The ratchet wrench is useful for driving a fastener used in dentistry, such as an abutment screw which holds an abutment on a dental implant. In operation, the handle of the wrench can be rotated in one direction (e.g. clockwise) to impart torque on the fastener. When the handle is rotated in the opposite direction (e.g. counterclockwise), no torque is applied to the fastener as the handle is returned to a position where it is easy for the clinician to again rotate the handle to apply additional torque to the fastener.
The return motion of the handle (e.g. counterclockwise rotation) may be stepless in operation which is brought about through a coiled clutch spring located in an annular space within a housing between the housing and a concentric driver member. The clutch spring has one end fixed to one of the housing and the driver member and the other end free in the annular space between them. Preferably, the part of the annular space containing the free end is thinner than the part of the annular space containing the fixed end of the clutch spring. Depending on the direction in which the clutch spring is coiled, its free end will slip in the annular space when relative rotation around is imparted in one direction between the housing and the driver member. However, it will latch the housing and the driver member against relative rotation in the opposite direction. Alternatively, the return motion of the wrench can be accomplished by using an overrunning or detent clutch which provides a xe2x80x9cclickxe2x80x9d-type action.
To provide an indication of torque, a rotor body is supported coaxially within the driver member. A torsion spring located between the rotor body and driving member is fixed at one end to the rotor body and at its other end to the driving member. This rotor body is adapted to hold one or more wrench tools in one or more sockets located on the common axis. Torque indicator marks on the rotor body and the driver member indicate angular displacement of the driver member around the common axis relative to the rotor body when a tool held in the rotor body is restrained from turning under load. The housing and with it the drive member may be turned by hand around their common axis when the housing is turned in the latched direction. Or, a handle fixed to the housing may be used to turn the housing around the common axis. The torque indicator marks indicate torque at the axis of rotation of a tool. The fixed handle does not participate in this measurement, and can therefore be of a simple, stiff design. The rotor body may be provided with a receptor for an ISO-type dental latch, as well as a socket or receptor for another type of tool.